So what is the difference? What exactly is "HID" defined as?
Does HID simply mean it is brighter or that it more closely matches natural sunlight than traditional bulbs or halogens?
It hard to what is needed, since some of the systems have a bunch of electronics, some have a new headlight shell, and some have just a bulb. Also, some cost 500$ while others only cost 50$.
I have halogens now, but wouldn't mind upgrading later.